Centering device



Dec. 10, 1940. J. KARTARIK CENTERING DEVICE' v Filed ot. 2'?, 195s Patented Dec. 10, 1940 UNITED sTATEs PATENT OFFICE CENTERING DEVICE Joseph Kartarik, St. Paul, Minn. Application October 27, 1939, Serial No. 301,665

2 Claims.

This invention relates to an improved centering device for drill bits, and the primary object of the invention is to provide a novel bit attachment adapted to accurately center a hole formed by a bit in a piece of iWork, relative to a countersunk opening in a member attached to the work.

A more specic object of the present invention is to provide a bit attachment of the above kind which may be readily applied to a drill bit, and

which may be eiectively clamped, together with the drill bit, Within the chuck of a brace at a single operation.

A still further object of the present invention is to provide a centering device of the above kind which is simple in construction, durable, and

eiiicient in use.

Other objects of the present invention will become apparent from the following description when considered in connection with the accompanying drawing, inwhich:

Figure 1 is an elevational view of a drill bit equipped with a centering device constructed in accordance with the present invention.

Figure 2 is a longitudinal sectional view thereof taken on line 2- 2 of Figure 1.

Figure 3 is atop plan view of the same; and Figure 4 is a transverse section online @-4 of Figure 1.

Referring in detail to-the drawing, the pres- 3o ent centering device comprises a tubular member through which the conventional drill D is adapted to be directed, and which is preferably composed of an upper section 5 whose lower end is in the form of an internally threaded cap 6. The remaining portion of the upper section 6 is in the nature of a reduced shank l rigid with and projecting upwardly. lfrom the cap portion 6 and split longitudinally at a plurality of points as at 8. The shank l is adapted for reception in:

4 the chuck of an ordinary brace, and by splitting the shank as at 8, said shank is capable of compression under the inuence of the Jaws of the brace chuck for effecting the equipped clamping action of the shank 'l upon the drill D, whereby said drill and the centering device may be locked in the chuck at a single operation.

The centering device further includes an intermediate section 9 in the form of a cylinder having anopen upper end threadedinto the cap portion 6 of the upper section and provided with abottom wall having a 'central opening at I0. The centering device further includes a lower section II slidable through the bottom opening I0 of the intermediate section 9 and having an 55 external annular ange ,I2 at the top thereof (Cl. T1-55) arranged to abut the bottom wall of the intermediate section 9 to limit the downward movement of the lower section II under the iniiuence of a helical compression spring I3 arranged in the intermediate section 9 and having its ends 5 respectively abutting the top wall of the cap portion 6 of the upper section 5 and the upper end of the lower section II. In this way, the lower section lII is yieldingly projected substantially ush with the lower end of the drill D, and 10 the lower end of the lower section II is tapered or of conical form as at I4 to provide a nose adapted to enter the countersunk opening of a member and thereby direct the drill bit D perpendicularly to this member precisely at the cen- 15 ter of the countersunk opening. Thus, when the drill bit D is used to form an opening in the work, such opening will be accurately centered with respect .to the countersunk opening of the member referred to, the lower section II of the 20 centering device receding as the drilling proceeds as permitted by the spring I3; The lower and intermediate sections II and 9 are provided in the sides with openings I5 and I6, respectively to permit the escape of drilling outwardly there- 25 through in case the same should nd their way l into said sections II and 9 of the device.

The present invention will be found of great value when it is desired to fasten a-metal plate onto a backing by screws, which plate is drilled 30 and provided with proper countersinks for the screw heads. AIn order that the screws shall have their heads rest flush with the surface of the plate when they are screwed home, it is necessary that the screws be started exactly in the 35 center of the countersunk hole, as well as accurately perpendicularly to the plate. Otherwise, the head or one side thereof would project above the plate. By means of the present attachment,

' this true centering can be readily and accurately 40 performed without depending upon the skill and vjudgment of thevmechanic. 'I'he device is extremely simple, convenient to use, and efcient. While I have shown what I believe to be a preferred -embodiment of the present invention, it 45 Vwill-be understood that the same is capable of l various modifications and changes in specic details of construction. i y

While the main purpose of the present inven- 50 tionis to center a drill bit as above described; it will be noted that the device acts as a guide which braces the drill bit against deiiection and breakage. Also, by varying the position of the drill bit longitudinally with respect to the device, the latter will act to regulate the depth of drilling. y

What I claim as new is: 1. A centering device for drill bits comprising 'a tubular member through which the drill bit is adapted to be directed, said tubular member comprising an upper section reduced at its upper end to provide a shank, and a spring projected .lower section having a conical lowerV end` providing a nose adapted to enter a countersunk opening with which an opening to beformed by the .drill is adapted to bel centered, said-shank being split longitudinally so as to be capable of compression whereby the centering device and drill may be secured in a chuck at a single operation, said uppersection consisting of an in- 4ternally threaded cap having the shank rigid cap portion and the top of said lower section.

2. A centering device for drill bits comprising a tubular member through which the drill bit is adapted to be directed, said tubular member comprising an upper section reduced at its upper end to provide a shank, a spring projected lower section having a conical lower end providing` a lnose adapted to entera countersunk opening with which an opening to belformed by the drill is adapted to be centered, said shank being split longitudinally so as to be'capable of compression whereby the centering device and drill may be secured in a chuck `at a single operation, said upper section consisting of an internally threaded caphaving the shank rigid with and project- -ing upwardly therefrom, a cylindrical intermediate section threaded into said cap at its upper end and havinga central opening in Ithe bottom thereof through which the lower section slidably projects, said lower section having' an external y annular iiange on the upper end thereof. ar-

ranged to abut the bottom o'f the intermediate Isection to limit the projection of said lowerfsection, and a helical compression spring` arranged in the intermediate section and having its ends respectively bearing against said cap portion and the top of said lower section, said lower and intermediate sections having openings through the sides thereof for the escape of drilling.

- JOSEPH KARTARIK 

